1. Field of the Invention
The present invention relates to a novel acrylic acid ester derivative having a triphenylamine skeleton, a polymer comprising such an acrylic acid ester moiety as repeat unit, and an electrophotographic photoconductor comprising a substrate and a photoconductive layer formed thereon, which comprises the above polymer.
2. Discussion of Background
Recently, organic photoconductors (OPC) are widely used in copying machines and printers. Such organic photoconductors comprise, for example, a substrate and a photoconductive layer. The photoconductive layer may comprise a charge generation layer (CGL) and a charge transport layer (CTL) which are successively overlaid on the substrate. The CTL is in the form of a film which comprises a low-molecular-weight charge transporting material (CTM) dispersed in a binder resin in a certain concentration. The addition of the CTM to the binder resin causes deterioration of the mechanical strength of the binder resin itself. The CTL is fragile and has a low tensile strength. It is considered that the above-mentioned deterioration of the mechanical strength of the binder resin causes some problems in the photoconductor, such as wear, flaw, peeling, and crack.
There have been proposed many photoconductors in which a high-molecular-weight material such as polyvinyl anthracene or polyvinyl pyrene is singly used as a charge transporting material in the CTL. However, these photoconductors comprising the above-mentioned high-molecular-weight charge transporting material do not have sufficient mechanical strength or electrical characteristics.
A photoconductor comprising an acrylic polymer in the CTL is described by M. Stolka in J. POLYM. SCI. VOL. 21, 969. When this acrylic polymer is employed in the CTL, the charge mobility is so low that a sufficiently high photosensitivity for use in practice cannot be obtained.
Furthermore, a photoconductor in which a vinyl polymer of hydrazone is used in the CTL is disclosed in '89 JAPAN HARD COPY p. 67. This photoconductor has a relatively high residual potential.
Photoconductors comprising carbazole polymers described in Japanese Laid-Open Patent Applications 1-115915, 1-141902, and 1-141939 have low photosensitivities. Although the photoconductors described in Japanese Laid-Open Patent Applications 1-134456, 1-134457, and 1-134462 have good photosensitivity, they have problems in the residual potential and in the changes in the photosensitivity. In addition, the compounds described in Japanese Laid-Open Patent Application 64-9964 cannot be easily synthesized, and therefore are not suitable for use in practice.